1. Field of the Invention
The present invention pertains to an optical apparatus and more particularly to an optical apparatus which is arranged to provide a water prism having arcuately adjustable side walls for forming lens faces on said prism.
2. History of the Prior Art
Water prisms have long been known as an apparatus for refracting light waves propaged through such a prism. Water prisms themselves at least go back to the time of Johann Wolfgang Von Goethe (1749-1832) who used water prisms to study the spectural effects on light passing through the refracting surfaces of the prism. It was early discovered that a water prism was less expensive to construct because it did not involve the forming of a primodic shape from a solid material having optical qualities but rather only required flat glass surfaces forming a triangularly shaped closed container which could be filled with a liquid medium such as water to provide the body of the prism. Typically in such water prisms, a means was provided for filling and emptying the prism. A prism such as described above is shown in U.S. Pat. No. 71,309 which was granted to Bart Kane on Nov. 26, 1867.
Another U.S. Pat., No. 1,264,374 which was granted to Luis de Florez on April 30, 1918, shows a liquid filled prism having rigid closed sides and which included a system for varying the density of a medium filling the prism and thereby varying the refraction of light waves passing through the prism. The density of the fluid medium is varied by varying the pressure of the fluid filling the prism.
R M. Pierson, in U.S. Pat. No. 2,483,102, shows a refractometer for automatically measuring and monitoring the refractive quality of a given fluid which might be caused by changes in pressure, temperature, or chemical properties of the fluid. The Pierson device has rigid enclosed walls and utilized a photosensitive device to monitor the refractive angle of a beam of light passed through the prism.
On Apr. 11, 1971, U.S. Pat. No. 3,655,274 issued to D. R. Graig shows a gravity operated liquid filled prism device comprised of two enclosed chambers, each having a boat positioned therein, with the boats being constructed of optical materials. The effect of gravity on the angular position of the optical boats is used to make corrections in roll movements of vehicles, for directing a plumb, or for vertical visual orientation.
All of the prior art devices described above are constructed with rigid side walls for enclosing a liquid and do not provide for the convenient changing of the fluid material and convenient cleaning of the interior surfaces of the prism if it is desired to change from one fluid to another. In addition it is also not possible to readily remove small air bubbles which form on the side walls of the prism and which tend to alter the optical qualities of the side walls. Also, the rigid construction of the side walls does not permit any angular deviation of the side walls, should this be desirable. U.S. Pat. No. 3,606,523 to G. W. Taylor entitled "Fluid Variable Light Deflector", discloses apparatus for selectively changing fluids including using air under pressure to purge fluids from a liquid filled lens or prism, such fluids having differing refractive indices so as to vary a light path passing through such lens or prism.
Another patent which discloses a fluid filled lens is U.S. Pat. No. 1,739,478 to Bielecki. A series of tubes and valves are connected to a lens so that fluids of varying color and density are used to fill the body of the lens in order to vary the color of light passing through the lens.
O'Leary Pat. No. 2,504,039 shows an adjustable fluid prism wherein the ends, tops and bottoms of the prism are consructed of a bellows-like material which permits the angular adjustment of a pair of transparent panels making up prism walls. A gas or fluid fills the adjustable bellows and light is passed through the transparent panels to vary the refraction of light therethrough for producing a three-dimensional effect in optical applications.
The prior art does not provide a fluid filled optical device whereby a liquid filled prism is open to provide for easily changing the fluid therein and for mechanically cleaning the inner optical walls of the prism. Since one of the purposes of changing fluids in the prism is to provide a variation of optical parameters in relation to varying properties of the fluids, it is therefore important to be able to not only completely purge the replaced fluid from inside the prism, but to further mechanically remove the fluid from the inner surfaces of the prism so as not to leave a residual fluid on the optical wall of the prism. In addition, the formation of bubbles on the optical walls is readily remedied if one can mechanically scrape the interior prism walls. By having a prism system which permits ready access to the interior optical walls of the prism, this advantage is accomplished.
A further drawback of prior art devices relates to the absence of a means for varying the radius of curvature of the walls of a prism and thereby provide a means for adjusting the optical configuration of the walls of a prism. Such a provision for varying the light bending characteristics of the walls enhances the experimental aspects of an optical prism device as well as providing an infinite range of variability to the modification of light transmission through the optical device, so that not only can the fluid body of the prism be varied and therefore the optical qualities of the prism thus associated, but also the surface of the prism walls can be curved through an infinite range to thereby also modify its optical qualities. It is with these criteria of features in mind that the present invention has evolved.
The devices shown herein as prior art, in addition to the shortcomings set forth above, do not offer the combination of optical variations which are needed to provide the experimental characteristics of the optical device of the present invention. Another general drawback of such prior art devices is their complexity of structure and design. It is one of the major objects of the present invention to provide an inexpensive yet effective device for performing a variety of optical experiments and to give the experimenter, and in particular the younger science student, the ability to provide a myriad of optical variations so as to go beyond the "standard" optical experiments. To provide an inexpensive apparatus to this end is most important and is effectively achieved with this invention.